1. Field of the Invention
The present invention relates to the manufacture of books and particularly to the movement of partially completed books from station-to-station in a bookbinding process. More specifically, this invention is directed to a transport channel which guides book blocks, standing upright and supported laterally, as they are caused to slide along a surface while travelling between work stations. Accordingly, the general objects of the present invention are to provide novel and improved methods and apparatus of such character.
2. Description of the Prior Art
Book block transport channels of the general type to which the present invention is directed are well known in the art and are often employed as entry sections for bookbinding machines. The known transport channels are defined by a pair of lateral guides, which form the channel side walls, and a vertically adjustable book block skid plate, which forms the channel floor. The skid plate is located between the guides and, during movement, the book blocks are caused to slide along the channel, while resting on the skid plate, by pusher elements associated with a conveyor. The distance between the lateral guides of a book block transport channel must be variable to accommodate different book block thicknesses. The requirement of adjustability of the lateral guides, in turn, dictates the need to match the skid plate or plates to the spacing between the guides. In the prior art, the matching of the width of the book block skid plates to the lateral guide spacing has been accomplished by changing the skid plates.
The changing of book block transport channel skid plates results in long machine set-up times because there is no easy access to the plates for the purpose of removal and reinstallation. Long machine set-up and change-over time is becoming increasingly intolerable in the bookbinding art for several reasons. Firstly, the changing of the book block skid plates requires trained personnel, is labor intensive and thus is expensive. Secondly, long set-up time is an impediment to increases in productivity, by increasing book block through-put, while retaining current production techniques. Thirdly, the number of copies of a book produced per print run has been continually declining in recent years thereby requiring more frequent changes in machine set-up. It is also to be noted that the necessity of skid plate replacement requires that a multiplicity of skid plates of varying width be maintained in inventory.
To expand somewhat on the above remarks, a very large number of finely graded book block skid plates are typically required in order to achieve exact matching of the skid plate to the distance between the lateral guides of the book block transport channel, this distance being set to suit the thickness of the book blocks which are to be processed at any given time. In practice, however, cost considerations make it impossible to maintain the requisite large skid plate inventory. Accordingly, gaps often occur between the skid plate and the lateral guides. When thick, unstable book blocks are being processed, the outside portions of such blocks can sag into these gaps, become wedged therein and consequently cause production stoppages or malfunctions. The interference between the outside portions of a book block and the gaps in the transport channel is especially a problem when the conveyor pusher elements contact the book blocks above their center of gravity thus producing a tilting moment.